ANKARA, March 5 (Xinhua) -- Turkish police on Monday detained four Islamic State suspects in northern Samsun province, as part of an investigation into a possible attack on the U.S. embassy in Turkey.

The four suspects detained were all Iraqi citizens and were taken to the police station for legal proceedings, state-run Anadolu Agency reported.

Early Monday, Ankara police detained 12 IS suspects in raids across the city, accusing them of trying to recruit members for IS and "contacting with people in conflict zones."

The U.S. embassy was closed on Monday due to an unspecified security threat. Police have taken high security measures outside the U.S. embassy.